Custom Form Input not binding to model

Question

I am trying to make a custom form input in Angular 4. This is a simple example, but I cannot get the component to bind to the ngModel. I can pass this component a default value from the parent controller, but when I change a value in this input, the UI registers the change, but the model in the controller is not showing the new value.

Here is my custom component:

import { Component, Input, forwardRef, Output, EventEmitter, ElementRef, Renderer } from '@angular/core';
import { ControlValueAccessor, NG_VALUE_ACCESSOR, NG_VALIDATORS, FormControl } from '@angular/forms';

@Component({
    selector: 'input-test2',
    template:
        `
           <input type="text" class="form-control" placeholder="Symbol"  [(ngModel)]="value" [maxlength]="5" >     
        `,
    providers: [
        {
            provide: NG_VALUE_ACCESSOR,
            useExisting: forwardRef(() => InputTestComponent),
            multi: true
        },
    ]
})
export class InputTestComponent implements ControlValueAccessor {
    @Input('value') value = false;
    
    private propagateChange = (_: any) => { };
    private propagateTouch = (_: any) => { };
    
    writeValue(value: any): void {
        if (value) {
            this.value = value;
        }
    }
    
    registerOnChange(fn: (_: any) => void): void {
        this.propagateChange = fn;
    }
    registerOnTouched(fn: () => void): void {
        this.propagateTouch = fn;
    }
    
    private onChange(event : any) {
        this.propagateChange(this.value);
    }

And my usage of the component: .. inside a form

<input-test2 id="coin" name="coin" [(ngModel)]="manualEntry.coin" #coin="ngModel" required (change)="x($event)" > </input-test2>

Does anyone have a simple example of how to do this custom form input? All examples I found are either complex and leave out functionality. I just want a default input type="text" to start with and then I can add to this.

Answer 1

Thanks for the comments above. Now working as expected. This seems to be a good snippet that provides a basic implementation of input type="text":

import { Component, Input, forwardRef} from '@angular/core';
import { ControlValueAccessor, NG_VALUE_ACCESSOR} from '@angular/forms';

@Component({
    selector: 'input-test2',
    template:
        `
           <input type="text" class="form-control" placeholder="Symbol"  [(ngModel)]="value" [maxlength]="5" (change)="onChange($event)" [disabled]="isDisabled" >     
        `,
    providers: [
        {
            provide: NG_VALUE_ACCESSOR,
            useExisting: forwardRef(() => InputTestComponent),
            multi: true
        },
    ]
})
export class InputTestComponent implements ControlValueAccessor {
    @Input('value') value = false;
    
    private propagateChange = (_: any) => { };
    private propagateTouch = (_: any) => { };
    private isDisabled: boolean = false;
    
    constructor(){

    }
    writeValue(value: any): void {
        if (value) {
            this.value = value;
        }
    }
    
    registerOnChange(fn: (_: any) => void): void {
        this.propagateChange = fn;
    }
    registerOnTouched(fn: () => void): void {
        this.propagateTouch = fn;
    }
    
    private onChange(event : any) {
        this.propagateChange(this.value);
    }

    private onTouch(event : any){
        this.propagateTouch(event);
    }

    setDisabledState(isDisabled: boolean): void {
        this.isDisabled = isDisabled;
      }



}

And usage of this component can be used in a form like this:

<input-test2 
       type="text"  
       id="coin" name="coin"  
       [(ngModel)]="manualEntry.coin"  
       #coin="ngModel" 
       required [disabled]="false" 
       (change)="test($event)">
</input-test2>

I wish there were better instructions on this as I feel like this is a fairly common practice to create custom/reusable components in forms.